Normally these are outdoor spiders, but sac spiders often invade structures (like my house). Their numbers increase significantly in the Autumn when the weather turns cool and their food supply disappears.
If there is food available, sac spiders can become established indoors. At night they actively search for small insects. When hunting, they run quickly while waving their forelegs in front of them. Their front legs are longer than their other three pairs of legs.
Indoors, they can be observed on walls and ceilings, but they quickly drop to the floor and seek cover when disturbed. Yellow Sac Spiders construct a silken tube or sac in a protected area, such as within a leaf, under a log, or at the junction of a wall and ceiling.
They use this sac as their daytime retreat; this is how the sac spider gets its name. These spiders do not build webs. Outdoors, this species occupies a wide variety of habitats, including trees, the forest floor, fruit orchards and other agricultural areas, as well as shrubs surrounding open fields.
These creatures are usually pale in color and can range from yellow to beige. They are quite small (about 1/2 inch long) and easy to overlook, with no distinct markings.
This species has eight simple eyes aligned in two rows of four, consisting of secondary and primary eyes. Secondary eyes are light sensitive and are used to track movement. Primary eyes are the only set of movable eyes and are used to view close objects.